Measuring the Earth’s albedo with simple instruments

The Earth’s albedo, as the fraction of sunlight that is directly reflected back into space from the surface or clouds, is a key factor in modeling Earth’s climate. In tasks such as the simplified estimation of the mean temperature, it is usually given as a constant, without mentioning its determination and the associated difficulties. In fact, the albedo can be determined by a basically simple procedure based on the observation of a well-known phenomenon: Earth’s shine. A comparison of the intensities between the directly illuminated side of the Moon and the side illuminated by Earth’s shine provides the mean albedo for a large part of the Earth’s surface. In this paper, the procedure will be reproduced using simple instruments. Assuming the reflection properties of a Lambert sphere—an ideal diffuse reflecting body—for the Earth, and using measurements of the phase function—as a description for the angular distribution of the scattered light—of the Moon, the Earth’s albedo is determined from self-acquired data. Even with these simple conditions it is possible to come quite close to the value of the Earth’s albedo.